Catalytic hydrogenations are employed to add hydrogen over double and triple bonds. As an example, catalytic hydrogenation of vegetable oils is employed to change the physical properties, such as the melting point, of vegetable oils to obtain semi-solid fat suitable for use in the food industry.
Catalytic hydrogenations are also commonly used in the chemical industries, such as in petrochemical processes. Typically, expensive noble metals, such as platinum and palladium, are used as catalysts in catalytic hydrogenations. Different catalyst may display different selectivity towards different types of double and triple bonds. Further, the catalyst used is often supported by a carrier, such as carbon or alumina. Typically, the carrier is porous and the catalyst is distributed homogenously throughout the carrier, i.e. at both external and internal surfaces, to take advantage of the large surface area of the porous carrier.
The saturated aldehyde propionaldehyde, being an interesting building block in the petrochemical industry, may be obtained by selective gas phase hydrogenation of the corresponding 1,2-unsaturated aldehyde, i.e. acrolein.
It is well known within the art that palladium (Pd) has the ability to selectively catalyze the hydrogenation of 1,2-unsaturated aldehydes, such as acrolein and crotonaldehyde, to their corresponding saturated aldehydes, i.e. propionaldehyde and butyraldehyde (cf. Rase, H. F. Handbook of Commercial Catalysts. Boca Raton, CRC Press LLC, 2000. pp. 168-169; ISBN 0-8493-9417-1). Commonly employed catalysts for this reaction are Pd-on-carbon 5% in the slurry phase and 0.5% Pd on Al2O3.
As most catalysts within the art has been developed to produce the unsaturated alcohol (Claus, P. 1998, Topics in Catalysis, Vol. 5, pp. 51-62, P. Maki-Arvela, J. Hajek, T. Salmi, D. Y. Murzin. 2005, Appl. Catal. A. Gen., Vol. 292, pp. 1-49, and R. Hirschl, F. Delbecq, P. Sautet, J. Hafner. 2003, Vol. 217, pp. 354-366), a low cost selective catalyst for the production of the saturated aldehydes would be of interest.
Further, gas phase hydrogenation of for example acrolein in the presence of Pd on Al2O3 is not completely selective towards propionaldehyde, and ethene, as well as ethane, is formed, in addition to propionaldehyde. Thus, a more selective process would be desired.
Thus, there is need within the art for an method for producing saturated aldehydes, such as propionaldehyde, from 1,2-unsaturated aldehydes, such as acrolein, overcoming the above-mentioned deficiencies.